Glads for hardiness

Wed, 07 Mar 2007 05:08:21 PST
I have one of the orange-yellow flowered clones of G. dalenii that I
purchased from the Kirstenbosch plant centre while living in South
Africa.  It flowered for me regularly around March in the Cape, however,
upon returning to England it has so far eluded my best efforts.  The
first year I planted them out once the risk of frost was past but they
had not flowered prior to be lifted again in October - I put this down
to their acclimatising to the change in hemisphere.  The second year I
planted them out as early as I could but by November there were still no
signs of flowers, at which point there was a sudden sharp frost of
around -10oC, which caught me out badly with many of my plants.  The
foliage, and I presumed the bulbs, were finished, so I did not bother to
dig them up but left them in the ground to see if they would return of
their own accord.  Sure enough the following spring they did full of
vigour.  This year the weather was kinder and by the first weeks of
November, large flower spikes were beginning to appear.  The glow of
orange was on the buds, when at the beginning of December we had our
first frost, not particularly hard as the foliage appeared unaffected,
but it was enough to kill off all the flower spikes.
Clearly although the bulbs are hardy enough, the growing season is not
long enough (despite having an exceptionally hot summer last year) or
more likely, as the plants were certainly big enough by the end of
August, the flowering is triggered by the shortness of the day length.
It is interesting to see Tony's Gladiolus dalenii 'Halloweenie', which
is similar in coloration to my clone and from what he says in his
catalogue is also a late flowerer (not sure I agree with the description
of tacky - one needs bright and cheerful at that time of year in this
country).  It would be interesting to know how often the flower spikes
are lost before they emerge, possibly the growing season is just long
enough for him.
One of the remarkable aspects of the Dutch hybrids, most of which have a
good amount of G. dalenii in their parentage, is that they can grow and
flower so quickly from an April planting, therefore appear to be
unaffected by daylength.  It is clearly not just hardiness that we need
in new hybrids - see Jim's comments about making them suitable for
northern hemisphere growing seasons.
This year, I will try some in pots to bring into the greenhouse to
protect those flowerbuds from the frosts.

Christopher Whitehouse

Home: Cranleigh,Surrey,England,Zone 8

Dr Christopher Whitehouse
Keeper of the Herbarium
RHS Garden Wisley
Surrey GU23 6QB
Tel: 01483 224234
Fax: 01483 211750
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